Process for refining lead which contains bismuth



Patented June 18, 1940 PATENT orr ea PRO ESS FOR REFINING LEAD WHICHCONTAINS BISMUTH;

Jesse O. Bettcrton and Yurii E. Lebedeff,

.; K Metuchen, N. J., assignors to; American Smeltl i 1 ing and RefiningCompany, New York, N. Y.,

a ,ccrporation of New Jersey ticularymetal mixture or alloy andintroducing alkali, alkaline earth or rare earth metal reagents thereinfor the purpose of concentrating one or more of the constituents oftheoriginal alloy as v dross or crust which floats upon the molten bathand is readily separated therefrom.

However, early attempts to specifically apply the suggestionto the leadrefinery for the removal ofbismuth failed and the advent of anysuccessful, commercialprocesshad to await later discoveries, rjri'anyofwhich the readerwill find discussed or referred to in an article byapplicants appearing in Transactions of the American Ina stitut of"Mining and Metallurgical Engineers,

vol. 121,1pages 205 225 (1936).

Following the discoveries aforementioned, their principles weresoonadapted by various refineries treating thousands of tons annually oflead containing bismuth in the amounts ordinarily encountered which,asis well known, usually range in the neighborhood 'of a few hundredthsto afewftenths per cent. In this connection it is highly significant tonote that, insofar as applicants are aware, all of the refineriesreferred to employ calcium as a reagent in debismuthizing such lead.

The present invention provides a process for the removal of bismuth fromlead which renders the use of calcium unnecessary. This new process isbased upon the simultaneous action of magnesium and alkali metal whichaction was the more incapable of being predicted since none of thealkali metals alone produces any elimination of bismuth and magnesiumalone only produces a partial elimination of bismuth in alloyscontaining a high content thereof.

The process for deb-ismuthizing lead without the aid of calcium whichforms the subject of the present invention thus consists essentially inadding to lead which contains bismuth and which has been previouslymolten, magnesium and alkali metal in suitable quantities and thenallowing the metal bath to cool to near its temperature ofsolidification.

There is thus formed a floating crust containing bismuth, magnesium,alkali metal and lead and which is separated from the bath of metal byany known process.

This floating crust will contain, according to the proportions ofmagnesium and alkali metal used,

Application December 24, 1938,

Serial N0. 247,660

the desired part of the bismuth contained, and up i to substantially thewhole of the bismuth content.

After thistreatmentthe lead ordinarily contains an excessof magnesiumand alkali metal from which it can be freed by any known treatment, forexample, with chlorine.

For putting the process according to the invention into effect,themagnesium and alkali metal, e. g;, sodium, may be employed in thestate of pure metals or of alloys with lead or with other metals," andby adding successively or simultaneously to the bath of impure metal tobe treated. If desired, the proportion of magnesium or alkali metalutilized may be diminished and this ,,diminution be ,compensatedby anincrease of alkali met'algor magnesium taking care always to provide asimultaneous or successive addition of alkali metal andmagnesium; onemay thus in particular confer upon the refining process additionaladvantages such as, for example, minimum costs of the reagents employed,greater ease in the treatment of drosses, etc.

It may be noted that if the lead from which the bismuth isto be removedcontains, besides bismuth other impurities, these may be partly orwholly contained in the dross with the bismuth. However, as there areatpre'sent efiicacious means for the separation of these other currentimpurities from impure lead, it may be more economical to separate fromthe lead to be treated the greator part of its other impurities beforeapplying the process of the invention for the removal of hismuth.

The invention isillustrated in'the following non-limiting examples?Example I A lead containing 0.30% of bismuth is treated in the fusedstate with an' addition of magnesium equal to eight pounds per short tonand an addition of sodium equal to twelve pounds per short ton. Afteragitation and cooling to the neighborhood of the temperature ofsolidification, the floating crust is separated. The lead obtainedcontains only 0.007%, of bismuth.

Example II calcium used, the sole debismuthizing reagents being sodiumand magnesium in the first example and lithium and magnesium in thesecond example. The results are remarkable in view of the fact that nosubstantial reduction of bismuth could have been made in the lead of theexamples either with alkali metal or with magnesium, alone.

What is claimed is: I 1. Process for refining lead which contains.bismuth, consisting in adding to the lead-in the molten state magnesiumand alkali metal, cooling the metallic bath to the neighborhood of itssolidification point and then separating therefrom the floating crust inwhich the bismuth has collected, said process being performed in theabsence of calcium. I

2. Process for refining lead which contains bismuth without the aid ofcalcium, consisting in adding simultaneously to the lead in the moltenstate magnesium and alkali metal, cooling the metallic bath to theneighborhood of its solidification point and then separating therefromthe floating crust in which the bismuth has collected.

3. Process for refining lead which contains bismuth without the aid ofcalcium, consisting in adding successively in either sequence to thelead in the molten state magnesium and alkali metal,

cooling the metallic bath to the neighborhood of its solidificationpoint and then separating therefrom the floating crust in which thebismuth has collected. I

4. Process for refining lead which contains bismuth without the aid ofcalcium,-consisting in adding to the lead in the molten state magnesiumand alkali metal in the state of alloys with lead, cooling the metallicbath to the neighborhood of its solidification point and then separatingtherefrom the floating crust in which the bismuth has collected.

5. Process for refining lead which contains bismuth without the aid ofcalcium, consisting in adding to the lead in the molten state magnesiumand alkali metal in the state'of alloys with other metals, cooling themetallic bath; to the neighborhood of its solidification point and thenseparating therefrom the floating crustin which thebismuth hascollected. v r

the other.

7. Process for refining lead which contains bismuth, consisting inbringing to simultaneous action on the lead in molten state magnesiumand alkali metal, cooling the metallic bath to the neighborhood of itssolidification point and then separating therefrom the floating crust inwhich the bismuth has collected, said process being performed in theabsence of calcium.

.8. Process for debismuthizing lead which comprises mixing magnesium andalkali metal into a molten body of the lead, cooling same to raise acrust having a higher bismuth content than the original lead, andeffecting a separation between said crust and the refined lead, saiddebismuthization being effected without the aid of calcium reagent.

9. Process for refining lead containing bismuth a acterized in that theprocess is performedwithout the addition of calcium to the lead.

10. Process for refining lead with respectto bismuth as a contaminantwhich comprises subjecting the lead in molten state to the conjointaction of sodium and magnesium, concentrating the bismuth as abismuth-lead-sodium-magnesium product at a temperature favoring suchconcentration, and efiecting a separation between said product and therest of the lead, said process being carried out in the absence of anyei'fective amount of calcium reagent.

JESSE O.'BE1'1ERTON. YURII E. LEBEDEFF.

